Efficacy of human-managed milkweed (Asclepias sp.) dispersal methods to support monarch butterfly (Danaus plexippus) conservation
摘要
Milkweed (Asclepias sp.) loss in the United States has contributed to a significant decline in the size of the monarch butterfly (Danaus plexippus) overwintering population in Mexico. To support monarch conservation, milkweed restoration efforts are underway. One hands-on and low-effort strategy that is often implemented by public groups is making and dispersing seed balls, which are made of clay, compost, and milkweed seeds. This “throw-and-go” strategy for seed dispersal is an accessible method that has caught a lot of traction; however, uncertainty remains on the efficacy and germination rates of milkweed seeds imbedded within seed balls. This study assessed the impact of seed balls on milkweed germination rates in an incubator. In a seed tray, milkweed seed was planted for three dispersion methods: seed balls, seed paper, and bare seed. Each method contained either common (Asclepias syriaca) or butterfly milkweed (Asclepias tuberosa), with either stratified or unstratified seed. Common milkweed had a higher number of seeds to germinate per replicate for stratified than unstratified seeds. Bare seed and those in seed paper had higher germination rates than those in seed balls. Germination rates for stratified butterfly milkweed seeds were lower in seed balls compared to seed paper.
Implications for insect conservationThese results suggest that alternative hands-on methods of milkweed seed dispersal, like making seed paper, may be more germination-efficient to support monarch butterfly conservation than seed balls.